.Children that exhibit co-occurring conduct problems and depression are at increased risk for substance abuse, delinquency, violence, and suicide. Once these co-occurring problems have developed, they are typically difficult to modify. The candidate seeks a career award to examine the roles of peer-child interactional and prefrontal processes in the development of co-occurring conduct problems and depression. Peer-child interactional and prefrontal processes are prospectively linked to conduct problems and depression, potential precursors for other risk factors, and identifiable and potentially modifiable in school, the primary venue for many preventative interventions. Person- and variable-centered analyses will be conducted to examine alternative roles for these factors in the development of this comorbid condition. Several mentors with complementary skills will advise the candidate. Co-sponsor Dr. Nick lalongo will advise the Pi's training in longitudinal, person-centered modeling. Co-sponsor Dr. Jim Snyder will advise in peer-child observational analyses. Co-sponsor Dr. Larry Steinberg will advise training in developmental psychopathology models and contextual influences. Several consultants (and their areas of expertise) will provide assistance: Dr. Hongling Xie (peer relational processes), Drs. Charles Nelson and Daniel Pine (pediatric neuropsychology and cognitive neuroscience), Dr. Mike Stoolmiller (observational analyses), and Drs. Bengt Muthen and Tenko Raykov (statistics and methodology). The candidate will enroll in formal coursework to augment previous training and complement consultation in statistical modeling, person-centered analyses, and cognitive neuroscience. Coursework, in-person laboratory consultations, and secondary data analyses of peer-child interaction and prefrontal processes in the context of multiple comorbidity explanations during the first few years of the award will provide the groundwork for collection of pilot data. Later in the award, the candidate will examine peer-child processes through secondary data analyses and with additional consultations. The proposed project will provide the framework for the candidate's long-term goals of improved identification of peer- child and prefrontal mechanisms related to risk and resilience and longitudinal relations of conduct problems and depression. Such knowledge will inform etiological models and intervention efforts to limit the negative sequelae associated with this comorbid condition and promote positive development.